Ethiopia’s Prime Minister Meles Zenawi issued a blunt warning to opposition groups he says are trying to organize a people’s revolution. Mr. Meles on Tuesday accused the largest opposition coalition of serving as a cover for an outlawed rebel group.

In a nationally televised session of parliament, Mr. Meles had harsh words for the domestic opposition and for external forces he said are trying to destabilize Ethiopia. He served notice that his government would not tolerate anyone plotting demonstrations or terrorist attacks.

The legislative session had been called to hear the government’s six-month progress report. But when the only opposition lawmaker in the 547-seat legislature asked why supporters of the Medrek coalition are being arrested in the Oromia region, Mr. Meles responded that those in custody are suspected of being members of the outlawed Oromo Liberation Front.

Speaking in Amharic, Mr. Meles suggested that his government is aware of attempts to incite a people’s revolution. He blamed Medrek and its main component, the Unity and Justice for Democracy Party.

He said, "I would like to pass a message to Medrek, and particularly members of [the] Unity [for Justice and Democracy Party].

The Ethiopian leader said his government is not blind and deaf, and warned that anyone who takes part in what he called "the plot being hatched to incite protests and terror" would "pay a price."

Mr. Meles gave no details about what the plot might entails. But a campaign on the social networking website Facebook is calling for massive protests next month on the 20th anniversary of the day Mr. Meles’s Tigrayan People’s Revolutionary Front came to power.

Former Ethiopian President Negasso Gidada, who is chairman of the Unity for Democracy and Justice Party, denied any opposition involvement in planning the demonstration. In a telephone interview, he accused Mr. Meles of trying to suppress public protests by intimidating and demonizing the opposition as well as Ethiopia’s neighbors.

"We have not been involved in any kind of plot or in any kind of inciting protests and terror at any time, whether it is last week or this week or in the future - particularly not to incite terror. What he is saying does not apply to us, and it is only for us a threat to have it as a reason to prepare himself and his government to take illegal action against opposition party members," he said.

In his remarks to lawmakers, Mr. Meles accused two other countries in the region of trying to foment instability. He charged neighboring Eritrea with backing the Oromo Liberation Front, and he vowed to reciprocate by supporting rebels trying to overthrow Eritrean President Isaias Afewerki.

The Ethiopian leader also said he is not concerned about Egypt’s attempt to block funding for a massive dam to be built on the Nile River. Mr. Meles vowed last week that the $4.8-billion hydropower project would go ahead as planned, even though no international donor has agreed to provide financing.